The present invention relates to a rotor of a ventilated disk brake.
A ventilated disk brake is used to brake a rotating member such as a rotor rotating in response to rotation of a wheel or wheels by pressing it between a pair of brake pads, for example. In this respect, the ventilated disk brake is similar to a general disk brake. However, the ventilated disk brake differs from such a general disk brake because in the former the heat generated by friction between the rotor and the brake pads is radiated through a plurality of cooling ribs radially extending between the brake pad engaging walls of the rotor so as to increase the radiation efficiency.
FIGS. 1 and 2 show a conventional ventilated disk brake. A circular rotor body 1 has projections 2 at the inner edge thereof in which through-holes 3 are formed, respectively. The rotor body 1 is fixed to a hub portion of a vehicle wheel by bolts inserted into such throughholes. A pair of brake-pad engaging portions 1a are formed at the outer periphery of the rotor body 1. The rotor body 1 rotates in response to the wheels, and when the engaging walls 4, 5 of the rotor body 1 are pressed between a pair of brake pads (not shown), the rotor body 1 is braked by friction. As many cooling ribs 6 are formed to extend radially between the brake-pad engaging walls 4, 5, the heat generated by friction therebetween is transmitted to the ribs 6 and radiated therethrough into the atmosphere. Thus, the radiation efficiency is improved.
However, as shown in FIG. 1, in the conventional disk brake rotors, each of the cooling ribs 6 is uniform in size, shape and arrangement. For example, the thickness "t" of each cooling rib 6 is uniform. Also, each P pitch between the ribs 6 is uniform. Weight distribution at the circumference of the brake-pad engaging portion 1a of the rotor is uniform. As a result, as schematically shown by the uniformly distributed resonance waves "e" in FIG. 6 in which four-nodes natural resonance waves are illustrated, the resonance phenomenon easily occurs in the conventional disk brake rotor. For instance, as shown in FIG. 5, the impulse response characteristics a, b on the basis of some experiments indicate that the oscillation damping performance is very poor. In the experiments, the impulse of 100 g was given to a rotor with the diameter of 250 mm at a circle spaced from its center by 100 mm, and the oscillation was measured at the same place. The characteristics a, b mean that the oscillation has .+-.2.0 dB at the begining and is maintained at .+-. 0.3 dB 0.1 seconds thereafter. As can be seen from the foregoing, the conventional disk brake rotor has a very poor oscillation damping performance so that undesirable brake noise occurs. It results in decreasing of the disk brake commercial values.